Multicycle self-balancing gear pump

ABSTRACT

A multicycle self-balancing gear pump incorporates a variable staging valve for changing the amount of discharge flow of the pump. The pump employs seven gears with six gear meshes at pumping states and the variable staging valve controls both discharge and bypass porting of the pump. In one embodiment the staging valve is a rotary valve having a pair of valving members for controlling the discharge portion and a pair of valve members for controlling bypass porting. Another construction employs a linearly operated staging valve for controlling porting of the liquid flow.

[56] Relerences Cited UNITED STATES PATENTS 2,936,716 5/1960Looker........................ 418/200 X FOREIGN PATENTS 986,830 3/1965Great Britain................ 418/196 Primary Examiner-Carlton R. CrdyleAssistant Examiner-Richard J. Sher Arlorney- Hill, Sherman, Meroni,Gross & Simpson ABSTRACT: A multicycle self-balancing gear porates avariabl discharge flow with six gear in O United States Patent Pius J.Nasvytis East Cleveland, Ohio Appl. No. 8,861 [22] Filed Feb. 5, 1970[45] Patented Dec. 14, 1970 TRW Inc. Cleveland, Ohio 72] lnventor [73]Assignee m an mmwwmm m. i m mwnm m nS 30 5 D. e h D. mmv sd aeb "55 U SaW at 0.6 0 8 m m u m mwn n mna mtomem ne fhn p w m h a t ufiwfi m MPH Cem a ra WW8 v m 1 n g y Km n mum P .1 c p mm w m nu Q m .l 6 SP... e emea m hS t t 6 e n C am e m .m

e Pe valve controls both discharge and pair of valving members forcontrollin s41 MULTICYCLE SELF-BALANCING GEAR PUMP 214, 200 valve forcontrolling porting of the 1iquid flow.

MULTICYCLE SELF-BALANCING GEAR PUMP BACKGROUND OF THE INVENTION l. Fieldof the Invention This invention relates to pump apparatus, and moreparticularly to gear pump apparatus having a plurality of pumping stagesand adjustable valving for controlling liquid flow through the pump.

2. Description of the Prior Art Gear pumps are well known in the art andhave found particularly advantageous application as fuel pumps. Includedin this art is a type of gear pump in which a plurality of gears of evennumber form an endless annular train in which each gear is meshed with apair of adjacent gears. In designing such gear pumps, it' is difficultto accurately determine, and therefore reduce, the gear tooth load ofthedriving one of these gears. For example, in an eight-gear train inwhich the teeth of the eighth gear are engaged with the teeth of thefirst or driving gear, it is difficult to ascertain whether the eighthgear is being driven directly by the first gear or via the secondthrough seventh gears. Extremely good tolerances would then be requiredto determine if the eighth gear were actually driven by the first gearor the seventh gear. Also, since the eighth gear is driven by theseventh gear, there is a built-in leakage path between the gear teeth ofthe eighth gear and the first gear. This also true for any gear in sucha gear cluster. Accordingly, it is readily apparent that accuratedetennination and reduction of gear tooth load, highand low-pressurevalues and bearing loading in the design of such apparatus is difficult.These problems are further aggravated in gear pumps which are requiredto provide a variable delivery.

It is therefore highly desirable to provide, and a primary objection ofthe present invention to provide, a variable delivery gear pump which isfree of the above inherent problems.

SUMMARY OF THE INVENTION According to the invention, a variabledelivery, multicycle, self-balancing gear pump is provided with thegears in an open-ended cluster arrangement having an odd number of gearsand an even number of intermediate gear meshes. A gear pump constructedin accordance with the gear configuration of the present invention andemploying seven gears can be realized at a reduced size when compared tothat of a similarly rated conventional two-gear gear pump. The gear tipvelocity is a critical and sometimes limiting factor in the design ofgear pumps; therefore, since the cluster pump design reduces theindividual gear size, the pump speed may be increased from, say 7,800 to13,200 r.p.m. and still maintain the same gear tip velocity as found inthe conventional pump. A gear pump constructed in accordance with thepresent invention has the further advantages of less weight and lessvolume.

The gear loads resulting from the hydraulic pressure and gear meshes ofadjacent gears provides forces on the intermediate gear or gears whichnearly balance and produce a low resultant force. The load is thegreatest on the outboard gear due to the hydraulic unbalance around theperiphery of the gear, however, the resultant force may be accuratelydetermined during pump design and maintained within a reasonable andacceptable value.

The discharge flow of a pump constructed in accordance with the presentinvention may be varied by staging various gear meshes. According to oneembodiment of the invention, the discharge flow may be varied by arotary staging valve which opens and closes axial inlet and dischargeports. This rotary valve includes a plurality of valve members whichsimultaneously either open discharge valving members and close bypassvalving members, or close the discharge valving members and open thebypass valving members. Rotation of the valve is provided remotely froman engine control which supplies a rotational input to the valve to addor delete a pump stage in accordance with changes in engine flowrequirements.

According to another embodiment of the invention, the variable dischargeflow of the pump is provided by a linearly displacable valve in whichthe valve ports and flow passageways are selectively controlled to carryeither bypass flow or discharge flow at the command of a mechanicalmovement from the engine control, or by a transduced signal, such as apressure signal.

A further advantage of a gear pump constructed in accordance with theprinciples of the present invention resides in the amount of fueltemperature rise across a cluster gear pump having a staging valve ascompared to a conventional gear pump. Since the staging valve allows allbut one stage to bypass and operate without any pressure rise, thetemperature rise at low flow is that for a single stage pump which has,in the case of seven gears, one-sixth the capacity of the conventionalpump. This reduction in energy loss and high fuel turndown ratiosresults in a lower fuel temperature rise across the pump.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, and features of theinvention, its organization, construction and operation, will be bestunderstood from the following detailed description taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a sectional elevational view of a cluster gear pump accordingto an embodiment of the invention, the gear pump employing a rotarystaging valve having a plurality of valve members;

FIG. 2 is a sectional view of the gear pump illustrated in FIG. 1 takengenerally along the line II-II of FIG. 1;

FIG. 3 is a sectional view of the gear pump illustrated in FIG. 1 takengenerally along the line III-III of FIG. 1;

FIG. 4 is a sectional view of a gear pump according to a secondembodiment of the invention looking generally at a section of the pumpsimilar to that of FIG. 2 and particularly illustrating a linearlydisplaceable staging valve; and

FIG. 5 is a sectional view of the gear pump illustrated in FIG. 4particularly illustrating the flow passages between the gear stages andthe staging valve in a section immediately adjacent the area of thegears shown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 1, 2and 3, a multistage self-balancing gear pump is illustrated at 10 ascomprising a pump housing 11 including an inner housing section 12 andan outer housing section 13, generally spaced apart from the section 12but fluid sealed thereto. A booster housing section 15 is secured to thepump housing 14 by means of a plurality of machine screws 16 whichextend through aligned apertures 17, 18 and 19 of the pump elements 15,14 and 14, respectively. 1

The inner housing section 12 has formed therein a plurality ofcylindrical cavities or chambers 20a-20g arranged in an arcuatedisposition about the longitudinal axis of the inner section 12. Each ofthe chambers 20a-20g intersects adjacent similar chambers in fluidpassageways 26-31. Each of the chambers receives therein a rotatablymounted gear 32-38 the teeth of which mesh in the respective fluidpassageways 26-31 to provide the pumping function upon rotation of thegears.

The central intermediate gear 35 of the gear train 32-38 is drivinglyengaged with a rotatable drive shaft 39 for imparting rotary motion toeach of the gears 32-38.

A fluid inlet passageway 40 is provided for receiving fluid from a fluidsupply and delivering the fluid to the booster pump housing 15 whereinit is received in a chamber 41 and directed to a rotating impeller 42having a plurality of impeller blades 43 and 44. The impeller 42 issecured to the end 45 of the rotating shaft 39. The impeller includes asleeve 46 having a central bore for receiving the shaft end 45, thesleeve 46 being rotatably held by bearings 47 and 47a in the housingelements 15 and 14, respectively. The sleeve 46 includes a threaded endportion 48 which receives a nut 48a for securing the impeller 42 in thebooster pump assembly.

Rotation of the impeller 42 by the drive shaft 39 propels the fluid to achamber 49 having an outlet opening 50 through which the fluid isdelivered to a chamber 53 of the inner housing section 12 by way of anopening 51 in plate 14 and inlet opening 52 in housing section 12. Fluidto be pumped has therefore been provided to the inner housing section 12of the gear pump from the inlet passageway 40 to the chamber 53 by wayof a booster pump.

Referring specifically to FIGS. 2 and 3, fluid delivery to the pumpingstages is provided by way of a passageway 54 in the inner pump housingsection 12 in communication with the chamber 53 and in communicationwith a generally flat annular chamber 55 via a communicating cylindricalchamber 55a extending between the drive shaft 39 and the hollow portionof gear 35.

A plurality of fluid passageways extend between the chamber 55 and thepumping stages to provide fluid inlet and bypass flow for the pump. Aplurality of fluid inlet chambers 56-61 are provided in a generallyaxial direction between the chamber 55 and the individual pumpingstages. Each of these passageways has one end in communication with apassageway formed at the intersection of a pair of gear receivingchambers and another end which is ported into the main inlet chamber 55.For example, the fluid inlet chamber 56 includes a port 56a forpermitting fluid delivery to the other end 56b of the passageway whichcommunicates with the generally radial passageway 26 at the low pressureinrunning side of the gear mesh provided by gears 32 and 33 which aredisposed in chambers a and 20b, respectively. Each of the passageways56-61 therefore provides fluid delivery to the low-pressure areas oftheir respective pumping stages, that is at the inrunning sides of thegear meshes thereof.

At the outrunning sides of the gear meshes, that is at the high-pressureportions of the pumping stages, fluid is directed for delivery to theexterior of the pump. For example, at the outrunning side of the gearmesh of gears 37 and 38 the fluid under a high pressure is discharged byway of a port 62b to an outlet or discharge chamber 68 which is incommunication with the pump outlet 81.

The discharge port 62b is one of a plurality, in this case 3, of suchports 62b, 63b and 64b are also in fluid communication with the chamber55 by way of a corresponding plurality of passageways 62, 63 and 64which terminate at respective ports 62a (covered in FIG. 3), 63a and64a. The high pressure portions of the radially extending passageways26, 28 and 30 are also placed in communication with the chamber 55 byway of a plurality of passageways 65, 66 and 67, respectively. Each ofthese passageways terminate at respective ports 65a, 66a and 67a inchamber 55 at one end thereof and in the corresponding high pressureareas 65b, 66b and 67b at the other ends thereof, the passagewaysextending generally axially of the pump.

Fluid communication between the discharge ports 62b, 63b and 64b withthe chamber 68, and thus with the exterior of the pump, is controlled bymovement of a rotary valve 70 having a valve member 71 positionedbetween housing sections 12 and 13 and including a window 69 therein forcovering and uncovering the ports upon rotation of the rotary valve 70about the peripheral surface 86 of the inner pump housing section 12.The window 69 is positionable to sequentially uncover and cover theports 62b, 63b and 64b to vary the amount of fluid discharged to chamber68.

The valve member 71 of the valve 70 is connected for mu tual rotationwith a valve member 78. The inner pump housing section 12 includes acenter bore 76 having a sleeve 75 therein for rotatably receiving thevalve member 78. The valve member 78 is of generally tubularconstruction and includes a central bore 77 which is in communicationwith the fluid outlet 81 of the pump by way of a passageway 80 in theouter housing section 13.

A plurality of passageways 65, 66 and 67 are provided generally axiallyof the pump in the inner pump housing section 12 in communication at oneend thereof by means of valve ports 65a, 66a and 67a with the chamber55. A bypassing of fluid is provided through these passageways to thechamber 55 by selective rotation of the tubular valving member 78 toposition the window 79 thereof away from ports 65b, 66b and 67b whichcommunicate through openings 72, 73 and 74, respectively, with the fluidpassageway 77 for discharging fluid to the outlet 81. Rotation of thevalve 70 may effect an uncovering of these fluid channels at the window79 to provide a discharge path, while covering of these channelsprovides bypass of the fluid to the chamber 55 by way of the fluidpassageways 65, 66 and 67.

Selective rotation of the valve 70 is attained through the provision ofa plurality of teeth 88 on the periphery thereof for engagement withteeth 90 of a motor driven adjustment gear The fluid provided to thepump at passageway 40 has therefore beensubjected to the boosting actionof the impeller 42 and the pumping action of the gears 32-38 to providethe fluid at the outlet 81. Selective rotational positioning of thevalve 70 by means of the gear 89 positions the windows 69 and 79 toselectively cover and uncover discharge ports 62b, 63b, 64b, 65b, 66band 67b.

in addition, the selective positioning of the valve 70 also provides forcovering and uncovering of the aforementioned valve ports 56a-67a whichcloses off the respective axial passageways to insure passage of thefluid from the high pressure areas to the discharge passageways ratherthan back to the chamber 55.

Referring now to FIGS. 4 and 5, there is illustrated generally at amultistage gear pump which is somewhat similar to the gear pumpdiscussed above but which includes a linearly operated staging valverather than rotary staging valve.

The pump 100 comprises a housing 101 including a plurality ofgear-receiving chambers 102-108 of generally cylindrical form anddisposed in an arcuate pattern similar to that of the pump 10. Adjacentones of chambers 102-108 intersect in the area of radially extendingpassageways 109-114 and have individually disposed therein gears -121which form a serially connected gear train of which gear 118 is theintermediate driven gear, gear 118 being rotatably driven by a shaft122.

Extending somewhat axially of the pump are a plurality of fluidpassageways 123-128 which are placed in selective communication with afluid supply through a passageway 129 and a passageway 130 by means of astaging valve 131.

Passageways 123-128 each include an axial portion, such as portion 127a,which is in communication with another axial portion, such as 1270,through an intermediate portion, such as 127b, to further communicatewith an annular valve portion, such as 127d, fomted in the housing 101adjacent the staging valve 131. The axial portions 123e, 1280 arealigned with corresponding annular grooves 123d-128d and may operate aseither inlet or discharge passageways, 123s and 123d always beingdischarge passageways.

The staging valve 131 includes a hollow tubular member 132 having aplunger 133 slidably disposed therein and connected to a linearlyoperable shaft 134. The plunger 133 is fluid sealed to the interior wallof the tubular member 132 by means of an O-ring. Tubular member 132includes a plurality of ports 135-139 adjacent the grooves 123d-127d forpermitting fluid flow from passageway 130 to enter correspondingpassageways, such as 1270, which are to the left of the plunger 133. Thepassageways to the left of the plunger 133 therefore supply a fluidinput to the pump while passageways to the right-hand side of plunger133 are effective as discharge passageways to the chamber 123d whichsurrounds the plunger shaft 134.

Chamber 123d serves as the discharge passageway and is in communicationwith a relief valve by way of a passageway in a housing section 141which provides the discharge pressure against a valve member 142. Thevalve member 142 is adjustably biased by a spring 143 and threadedadjustment 144 to provide a selective relief pressure. The relief valvedoes not affect staging of the pump, but serves to provide a pressurerelease to channel fluid by means of fluid passageway 145 back to thefluid inlet of the pump.

Staging of the pump 100 may be accomplished by a mechanical movement ofthe rod 134 by an engine control, or by a pressure signal.

Generally then there has been provided a multistage gear pump withselective staging of the pump in one embodiment by a rotary valve, andin another embodiment by a linearly operated valve. The gear pumpincludes a plurality of gears connected in a serially innermeshedcluster with the intermediate gear of the cluster being driven to inturn drive the remaining gears. The gears are disposed in individualintersecting cylindrically shaped cavities into which fluid is portedfrom a booster pump stage to the gear pumping stages. Selectiverotational positioning of the rotary valve allows a predetermined amountof fluid discharge from the pump and a predetermined amount of fluidbypass from high-pressure to low-pressure portions of the pumping stagesby way of a fluid inlet chamber which serves as a common fluid feed toall pumping stages. In the case of a linear staging valve all dischargeflow from the pump is ported through the staging valve and a linearlyoperated piston is selectively positioned to control which portion of aplurality of fluid passageways are serving as inlet passageways andwhich portion are serving as discharge passageways.

Many changes and modifications may be made in the invention by oneskilled in the art without departing from the true spirit and scope ofthe invention and should be included in the appended claims.

What I claim is:

1. A multistage gear pump comprising:

a pump housing including means forming a plurality of cylindricallyshaped parallel intersecting chambers arranged in an arcuatedisposition;

a plurality of gears meshed to form a serial gear train with the gearsthereof disposed in and rotatably mounted in individual ones of saidchambers;

a drive shaft rotatably mounted in said housing and drivingly connectedto an intermediate gear of said gear train for rotating adjacent gearsin opposite directions, the rotation of said gears effecting lowpressure in portions of said chambers at the intersection of saidchambers adjacent the inrunning sides of the meshes of said gears andhigh pressure in portions of said chambers at the intersections of saidchambers adjacent the outrunning sides of the meshes of said gears;

a plurality of fluid delivery passageways in said pump housingcommunicating with said low-pressure portions of said chambers;

a plurality of fluid discharge passageways in said pump housingcommunicating with said high-pressure portions of said chambers;

staging valve means operable to alter the number of said delivery anddischarge passageways in communication with said plurality chambers;

a main fluid delivery passageway; and

a fluid delivery chamber in communication with said main fluid deliverypassageway and with said plurality of delivery passageways,

said staging valve means including a delivery valve operable to alterthe number of said plurality of fluid delivery passageways incommunication with said fluid delivery chamber.

2. A gear pump according to claim 1, comprising a plurality of bypasspassageways in communication with said fluid delivery chamber and withsaid high-pressure portions of said plurality of chambers, said stagingvalve means including a bypass valve operable to alter the number ofsaid bypass passageways in communication with said delivery chamber.

3. A gear pump according to claim 2, wherein said staging valve meansincludes a discharge valve operable to alter the number of dischargepassageways in communication with said plurality ofchambers.

4. A multistage gear pump comprising:

a pump housing including means forming a plurality of cylindricallyshaped parallel intersecting chambers arranged in an arcuatedisposition;

a plurality of gears meshed to form a serial gear train with the bearsthereof disposed in an rotatably mounted in individual ones of saidchambers;

a drive shaft rotatably mounted in said housing and drivingly connectedto an intermediate gear of said gear train for rotating adjacent gearsin opposite directions, the rotation of said gears effecting lowpressure in portions of said chambers at the intersection of saidchambers adjacent the inrunning sides of the meshes of said gears andhigh pressure in portions of said chambers at the intersections of saidchambers adjacent the outrunning sides of the meshed of said gears;

a plurality of fluid delivery passageways in said pump housingcommunicating with said low-pressure portions of said chambers;

a plurality of fluid discharge passageways in said pump housingcommunicating with said high-pressure portions of said chambers;

staging valve means operable to alter the number of said delivery anddischarge passageways in communication with said plurality chambers;

a main fluid delivery passageway; and

a delivery chamber in communication with said main fluid deliverypassageway and with said plurality of fluid delivery passageways;

each of said plurality of fluid delivery passageways including adelivery port opening into said fluid delivery chamber, and

said staging valve means including a delivery valve disposed in saiddelivery chamber and slidably operable to cover and uncover saiddelivery ports.

5. A multistage gear pump comprising:

a pump housing including means forming a plurality of cylindricallyshaped parallel intersecting chambers arranged in an arcuatedisposition;

a plurality of gears meshed to form a serial gear train with the gearsthereof disposed in and rotatably mounted in individual ones of saidchambers;

a drive shaft rotatably mounted in said housing and drivingly connectedto an intermediate gear of said gear train for rotating adjacent gearsin opposite directions, the rotation of said gears efl'ecting lowpressure in portions of said chambers at the intersection of saidchambers adjacent the inrunning sides of the meshes of said gears andhigh pressure in portions of said chambers at the intersections of saidchambers adjacent the outrunning sides of the meshes of said gears;

means for delivering fluid to said low-pressure portions of saidchambers including a main fluid delivery passageway,

a fluid inlet chamber in communication with said main fluid deliverypassageway, and a plurality of individual fluid delivery passagewaysextending between said fluid inlet chamber and separate ones of saidlow-pressure portions of said chambers; means for discharging fluid fromsaid high-pressure portions of said chambers including a main fluiddischarge passageway, and a plurality of individual dischargepassageways extending between separate ones of said chambers and saidmain discharge passageway; and staging valve means operable to alter thenumber of said individual delivery and discharge passageways incommunication with said chambers including first valve means interposedbetween said main delivery passageway and said individual deliverypassageway, and second valve means interposed between said individualdischarge passageways and said main discharge passageway. 6. Amultistage gear pump comprising: a pump housing including a generallycylindrical inner pump housing section,

a cup-shaped outer pump housing section spaced apart from said innerhousing section, and

means forming a plurality of cylindrically shaped parallel intersectingpumping chambers in said inner housing section in an arcuate dispositionwith their axes parallel to the axis of said inner housing section;

a plurality of gears meshed to form a gear train, each of said gearsbeing disposed in a separate one of said pumping chambers and rotatablymounted in said inner housing section;

a drive shaft connected to an intermediate gear of said gear train forrotating adjacent gears in opposite directions to effect low-pressureportions in said pumping chambers adjacent the inrunning sides of thegear meshes and high pressure portions adjacent the outrunning sides ofthe gear meshes;

a plurality of fluid delivery passageways in said inner housing sectionindividually communicating with said lowpressure portions of saidpumping chambers and having ports at one end of the inner housingsection;

a plurality of discharge passageways in said inner housing sectionindividually communicating with said high-pressure portions of saidpumping chambers and having ports at the peripheral surface of saidinner housing sections; and

a cup-shaped rotatable valve disposed in the space between said innerand outer pump housing sections operable to vary the number of saiddelivery and discharge passageways in communication with said pumpingchambers, said valve including a first valve member for opening andclosing the ports of said delivery passageways, and

a second valve member for opening and closing the ports of saiddischarge passageways.

7. A gear pump according to claim 6, wherein said'cupshaped rotatablevalve comprises a cylindrical portion embracing the periphery of saidinner housing section and having means forming a window therein forcommunication with the ports of said discharge passageways, and

an annular portion covering the end of said inner housing section havingthe ports of said delivery passageways therein, said annular portionincluding window therein for communication with the ports of saiddelivery passageways.

8. A gear pump according to claim 7, comprising a main deliverypassageway in said inner pump housing section, means forming an inletchamber in communication with said main delivery passageway includingthe ported end of said inner housing section and a shaped surface ofsaid annular portion of said valve spaced from the ported end.

9. A gear pump comprising:

a pump housing including I a generally cylindrical inner housing sectionhaving an annular end and a cylindrical peripheral surface,

an axial bore in said inner housing section,

means forming a plurality of cylindrically shaped parallel intersectingpumping chambers in said inner housing section in arcuate dispositionwith their axes parallel to the axial bore, and

an outer housing section having a cylindrical wall spaced from theperipheral surface of said inner housing section and an end wall spacedfrom the annular end of said inner housing section;

a plurality of gears each of which is rotatably mounted in separate onesof said pumping chambers, adjacent gears being meshed to form a geartrain;

a drive shaft connected to an intermediate gear of said gear train forrotating adjacent gears in opposite directions to effect low-pressurechamber portions adjacent the inrunning sides of the gear meshes andhigh-pressure chamber portions adjacent the outrunning sides of the gearmeshes;

means forming a fluid inlet chamber including said annular end of saidinner housing section and said end wall of said outer housing section;

a first fluid delivery passageway in said inner housing section incommunication with said inlet chamber;

' a plurality of second fluid delivery passageways individuallyextending between said annular end and said low-pressure chamberportions; means forming a first fluid discharge chamber including saidperipheral surface of said inner housing section and said cylindricalwall of said outer housing section; a first fluid discharge passagewayextending between said 1 first fluid discharge chamber and the exteriorof the P p a plurality of second fluid discharge passagewaysindividually extending between some of said high-pressure chamberportions and said peripheral surface of said inner housing section; aplurality of third fluid discharge passageways individually extendingbetween others of said high-pressure chamber portions and the axial boreof said inner housing section; a plurality of fluid bypass passagewaysextending between said high-pressure chamber portions and said annularend of said inner housing section, each of said second fluid deliverypassageways and said fluid bypass passageways having ports at saidannular end for communication with said inlet chamber; each of saidsecond and third discharge passageways having ports at the respectiveperipheral surface and axial bore; a rotary valve disposed in the spacebetween said housing sections and in the axial bore including firstvalve means positionable about said peripheral surface to open and closethe ports of said second fluid discharge passageways,

second valve means positionable along said annular end to open and closethe ports of second fluid delivery and fluid bypass passageways, and

third valve means positionable within the axial bore to open and closethe ports of said third discharge passageways, said third valve meansincluding a fourth fluid discharge passageway; and

a fifth fluid discharge passageway extending between said fourth fluiddischarge passageway and said first fluid discharge passageway.

10. The gear pump according to claim 9, wherein the ports of said secondfluid delivery passageways and said bypass passageways are arranged inarcuate disposition, and said second valve means includes arcuatesurfaces associated with the ports.

1 l. A multistage gear pump comprising: a pump housing; means forming aplurality of cylindrical parallel intersecting pumping chambers in saidhousing; a plurality of gears serially meshed to form a gear train andindividually rotatably mounted within said chambers; means for rotatingthe gears of said gear train; a fluid delivery chamber formed in saidhousing; means for providing a fluid flow to said delivery chamber; aplurality of first passageways connecting said delivery chamber to saidpumping chambers; means forming a discharge passageway in said housing;a plurality of second passageways connecting said pumping chambers tosaid discharge passageway; a plurality of third passageways furtherconnecting said second passageways with said delivery chamber; andstaging valve means disposed within said housing and including a firstvalve means operable to control the fluid coupling between said secondpassageways and said discharge passageway, and second valve meansoperable to control the fluid coupling by way of said first and thirdpassageways between said pump chambers and said delivery chamber.

12. A multistage gear pump according to claim 11, wherein said first andsecond valve means include an integrally formed structure and aretherefore concurrently operable.

1. A multistage gear pump comprising: a pump housing including meansforming a plurality of cylindrically shaped parallel intersectingchambers arranged in an arcuate disposition; a plurality of gears meshedto form a serial gear train with the gears thereof disposed in androtatably mounted in individual ones of said chambers; a drive shaftrotatably mounted in said housing and drivingly connected to anintermediate gear of said gear train for rotating adjacent gears inopposite directions, the rotation of said gears effecting low pressurein portions of said chambers at the intersection of said chambersadjacent the inrunniNg sides of the meshes of said gears and highpressure in portions of said chambers at the intersections of saidchambers adjacent the outrunning sides of the meshes of said gears; aplurality of fluid delivery passageways in said pump housingcommunicating with said low-pressure portions of said chambers; aplurality of fluid discharge passageways in said pump housingcommunicating with said high-pressure portions of said chambers; stagingvalve means operable to alter the number of said delivery and dischargepassageways in communication with said plurality chambers; a main fluiddelivery passageway; and a fluid delivery chamber in communication withsaid main fluid delivery passageway and with said plurality of deliverypassageways, said staging valve means including a delivery valveoperable to alter the number of said plurality of fluid deliverypassageways in communication with said fluid delivery chamber.
 2. A gearpump according to claim 1, comprising a plurality of bypass passagewaysin communication with said fluid delivery chamber and with saidhigh-pressure portions of said plurality of chambers, said staging valvemeans including a bypass valve operable to alter the number of saidbypass passageways in communication with said delivery chamber.
 3. Agear pump according to claim 2, wherein said staging valve meansincludes a discharge valve operable to alter the number of dischargepassageways in communication with said plurality of chambers.
 4. Amultistage gear pump comprising: a pump housing including means forminga plurality of cylindrically shaped parallel intersecting chambersarranged in an arcuate disposition; a plurality of gears meshed to forma serial gear train with the bears thereof disposed in and rotatablymounted in individual ones of said chambers; a drive shaft rotatablymounted in said housing and drivingly connected to an intermediate gearof said gear train for rotating adjacent gears in opposite directions,the rotation of said gears effecting low pressure in portions of saidchambers at the intersection of said chambers adjacent the inrunningsides of the meshes of said gears and high pressure in portions of saidchambers at the intersections of said chambers adjacent the outrunningsides of the meshes of said gears; a plurality of fluid deliverypassageways in said pump housing communicating with said low-pressureportions of said chambers; a plurality of fluid discharge passageways insaid pump housing communicating with said high-pressure portions of saidchambers; staging valve means operable to alter the number of saiddelivery and discharge passageways in communication with said pluralitychambers; a main fluid delivery passageway; and a delivery chamber incommunication with said main fluid delivery passageway and with saidplurality of fluid delivery passageways; each of said plurality of fluiddelivery passageways including a delivery port opening into said fluiddelivery chamber, and said staging valve means including a deliveryvalve disposed in said delivery chamber and slidably operable to coverand uncover said delivery ports.
 5. A multistage gear pump comprising: apump housing including means forming a plurality of cylindrically shapedparallel intersecting chambers arranged in an arcuate disposition; aplurality of gears meshed to form a serial gear train with the gearsthereof disposed in and rotatably mounted in individual ones of saidchambers; a drive shaft rotatably mounted in said housing and drivinglyconnected to an intermediate gear of said gear train for rotatingadjacent gears in opposite directions, the rotation of said gearseffecting low pressure in portions of said chambers at the intersectionof said chambers adjacent the inrunning sides of the meshes of saidgears and high pressure in portions of said chambers at theintersections of said chambers adjacent the outrunning sides of themeshes of said geaRs; means for delivering fluid to said low-pressureportions of said chambers including a main fluid delivery passageway, afluid inlet chamber in communication with said main fluid deliverypassageway, and a plurality of individual fluid delivery passagewaysextending between said fluid inlet chamber and separate ones of saidlow-pressure portions of said chambers; means for discharging fluid fromsaid high-pressure portions of said chambers including a main fluiddischarge passageway, and a plurality of individual dischargepassageways extending between separate ones of said chambers and saidmain discharge passageway; and staging valve means operable to alter thenumber of said individual delivery and discharge passageways incommunication with said chambers including first valve means interposedbetween said main delivery passageway and said individual deliverypassageway, and second valve means interposed between said individualdischarge passageways and said main discharge passageway.
 6. Amultistage gear pump comprising: a pump housing including a generallycylindrical inner pump housing section, a cup-shaped outer pump housingsection spaced apart from said inner housing section, and means forminga plurality of cylindrically shaped parallel intersecting pumpingchambers in said inner housing section in an arcuate disposition withtheir axes parallel to the axis of said inner housing section; aplurality of gears meshed to form a gear train, each of said gears beingdisposed in a separate one of said pumping chambers and rotatablymounted in said inner housing section; a drive shaft connected to anintermediate gear of said gear train for rotating adjacent gears inopposite directions to effect low-pressure portions in said pumpingchambers adjacent the inrunning sides of the gear meshes and highpressure portions adjacent the outrunning sides of the gear meshes; aplurality of fluid delivery passageways in said inner housing sectionindividually communicating with said low-pressure portions of saidpumping chambers and having ports at one end of the inner housingsection; a plurality of discharge passageways in said inner housingsection individually communicating with said high-pressure portions ofsaid pumping chambers and having ports at the peripheral surface of saidinner housing sections; and a cup-shaped rotatable valve disposed in thespace between said inner and outer pump housing sections operable tovary the number of said delivery and discharge passageways incommunication with said pumping chambers, said valve including a firstvalve member for opening and closing the ports of said deliverypassageways, and a second valve member for opening and closing the portsof said discharge passageways.
 7. A gear pump according to claim 6,wherein said cup-shaped rotatable valve comprises a cylindrical portionembracing the periphery of said inner housing section and having meansforming a window therein for communication with the ports of saiddischarge passageways, and an annular portion covering the end of saidinner housing section having the ports of said delivery passagewaystherein, said annular portion including window therein for communicationwith the ports of said delivery passageways.
 8. A gear pump according toclaim 7, comprising a main delivery passageway in said inner pumphousing section, means forming an inlet chamber in communication withsaid main delivery passageway including the ported end of said innerhousing section and a shaped surface of said annular portion of saidvalve spaced from the ported end.
 9. A gear pump comprising: a pumphousing including a generally cylindrical inner housing section havingan annular end and a cylindrical peripheral surface, an axial bore insaid inner housing section, means forming a plurality of cylindricallyshaped parallel intersecting pumping chambers in said inner houSingsection in arcuate disposition with their axes parallel to the axialbore, and an outer housing section having a cylindrical wall spaced fromthe peripheral surface of said inner housing section and an end wallspaced from the annular end of said inner housing section; a pluralityof gears each of which is rotatably mounted in separate ones of saidpumping chambers, adjacent gears being meshed to form a gear train; adrive shaft connected to an intermediate gear of said gear train forrotating adjacent gears in opposite directions to effect low-pressurechamber portions adjacent the inrunning sides of the gear meshes andhigh-pressure chamber portions adjacent the outrunning sides of the gearmeshes; means forming a fluid inlet chamber including said annular endof said inner housing section and said end wall of said outer housingsection; a first fluid delivery passageway in said inner housing sectionin communication with said inlet chamber; a plurality of second fluiddelivery passageways individually extending between said annular end andsaid low-pressure chamber portions; means forming a first fluiddischarge chamber including said peripheral surface of said innerhousing section and said cylindrical wall of said outer housing section;a first fluid discharge passageway extending between said first fluiddischarge chamber and the exterior of the pump; a plurality of secondfluid discharge passageways individually extending between some of saidhigh-pressure chamber portions and said peripheral surface of said innerhousing section; a plurality of third fluid discharge passagewaysindividually extending between others of said high-pressure chamberportions and the axial bore of said inner housing section; a pluralityof fluid bypass passageways extending between said high-pressure chamberportions and said annular end of said inner housing section, each ofsaid second fluid delivery passageways and said fluid bypass passagewayshaving ports at said annular end for communication with said inletchamber; each of said second and third discharge passageways havingports at the respective peripheral surface and axial bore; a rotaryvalve disposed in the space between said housing sections and in theaxial bore including first valve means positionable about saidperipheral surface to open and close the ports of said second fluiddischarge passageways, second valve means positionable along saidannular end to open and close the ports of second fluid delivery andfluid bypass passageways, and third valve means positionable within theaxial bore to open and close the ports of said third dischargepassageways, said third valve means including a fourth fluid dischargepassageway; and a fifth fluid discharge passageway extending betweensaid fourth fluid discharge passageway and said first fluid dischargepassageway.
 10. The gear pump according to claim 9, wherein the ports ofsaid second fluid delivery passageways and said bypass passageways arearranged in arcuate disposition, and said second valve means includesarcuate surfaces associated with the ports.
 11. A multistage gear pumpcomprising: a pump housing; means forming a plurality of cylindricalparallel intersecting pumping chambers in said housing; a plurality ofgears serially meshed to form a gear train and individually rotatablymounted within said chambers; means for rotating the gears of said geartrain; a fluid delivery chamber formed in said housing; means forproviding a fluid flow to said delivery chamber; a plurality of firstpassageways connecting said delivery chamber to said pumping chambers;means forming a discharge passageway in said housing; a plurality ofsecond passageways connecting said pumping chambers to said dischargepassageway; a plurality of third passageways further connecting saidsecond passageways with said delivery chamber; and staGing valve meansdisposed within said housing and including a first valve means operableto control the fluid coupling between said second passageways and saiddischarge passageway, and second valve means operable to control thefluid coupling by way of said first and third passageways between saidpump chambers and said delivery chamber.
 12. A multistage gear pumpaccording to claim 11, wherein said first and second valve means includean integrally formed structure and are therefore concurrently operable.